I've been a fan of legos my whole (short) existence and the greatest thing I've ever made was a Millenium Falcon from Star Wars: I have to say, those are some of the most awesome creations I have ever seen.

as a kid, i used to make a military base out of my blocks. but then i noticed that the newer kits you buy, the parts are uhhh making the construction simpler- instead of giving you 5 pieces that would give the desired shape, they gave you one, big. which made playing with it less fun. they are darn awesome still.

The most awesome thing I ever did with Legos was have an epic four-day mecha battle with my friend. He was pretty imaginative with that stuff, whereas mine all looked like large houses designed by a surrealist with a bad twitch... I loved playing with them, but I wasn't a very good designer.